In recent mobile communication systems, an Orthogonal Frequency Division Multiple Access (OFDMA) scheme and a Single Carrier-Frequency Division Multiple Access (SC-FDMA) scheme similar to the OFDMA scheme are actively researched as schemes useful for high speed data transmission in a wireless channel. In the multiple access schemes as described above, time-frequency resources for carrying data or control information are allocated and operated in a manner to prevent overlapping of the resources, to establish the orthogonality between users, so as to identify data or control information of each user.
In a cellular wireless communication system, it is an important factor to support a scalable bandwidth in order to provide a high speed wireless data service.
For example, a Long Term Evolution (LTE) system can have various bandwidths, such as 20/15/10/5/3/1.4 MHz. Service providers can select among the bandwidths described above to provide a service, and there are various User Equipment (UEs), ranging from UEs capable of supporting a maximum of a bandwidth of 20 MHz to UEs capable of supporting only a minimum bandwidth of 1.4 MHz. In addition, an LTE-Advanced (LTE-A) system targeted at providing a service of an IMT-Advanced requirement level can provide a broadband service up to a maximum of 100 MHz bandwidth through LTE Carrier Aggregation (CA).
For high speed data transmission, an LTE-A system employs a broader band than an LTE system. Since the backward compatibility for LTE UEs is also important, the LTE UEs should also be capable of accessing the LTE-A system to use a service provided by the LTE-A system. To this end, in the LTE-A system, the entire system band is divided into sub-bands or Component Carriers (CCs), also referred also to as cells, having a bandwidth that can be transmitted or received by an LTE UE. Predetermined CCs are combined and data is then generated and transmitted through each CC. Accordingly, the transmission/reception process of an LTE system according to the related art can be used for each CC to support a high speed data transmission of the LTE-A system. Each CC or cell can be classified into a primary cell or a secondary cell according to its use or importance in view of a UE. In view of a UE, there is only one primary cell and the other cells except for the primary cell correspond to secondary cells. In the LTE-A system according to the related art, an uplink control channel is allowed to be transmitted in only the primary cell while an uplink data channel is allowed to be transmitted in both the primary cell and a secondary cell.
Scheduling information for data transmitted through each CC is notified as Downlink Control Information (DCI) to a UE. DCI defines various formats and applies and operates a DCI format determined according to whether the scheduling information is scheduling information for uplink data or scheduling information for downlink data, whether a spatial multiplexing using multiple antennas is applied, whether the DCI is a DCI for power control, and the like. For example, DCI format #1, which corresponds to control information for downlink data to which the Multiple Input Multiple Output (MIMO) antenna is not applied, is configured by control information as follows.
Resource allocation type 0/1 flag: this control information notifies of whether the resource allocation scheme is type 0 or type 1. Type 0 applies a bitmap scheme and allocates resources by the unit of Resource Block Groups (RBGs). In an LTE or LTE-A system, a basic unit of scheduling is a Resource Block (RB) expressed by time and frequency domain resources and an RBG is configured by a plurality of RBs and serves as a basic unit of scheduling in type 0. Type 1 allows allocation of a particular RB in an RBG.
Resource Block assignment: This control information notifies of an RB allocated to data transmission. An expressed resource is determined according to the system bandwidth and resource allocation scheme.
Modulation and Coding Scheme (MCS): This control information notifies of a modulation scheme and a coding rate used in data transmission.
HARQ process number: This control information notifies of a process number of HARQ.
New data indicator: This control information indicates HARQ initial transmission or retransmission.
Redundancy version: This control information notifies of a redundancy version of HARQ.
TPC command for PUCCH: This control information notifies of a power control command for a Physical Uplink Control CHannel (PUCCH) which is an uplink control channel.
The DCI as described above is then transmitted through a Physical Downlink Control CHannel (PUDCH) which is a downlink physical control channel, after being channel-coded and modulated.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.